Abstract: The multiphysics algorithm in this paper is based on semiconductors physical model to realize the simulation of electromagnetic effects on semiconductor devices and circuits. The model is constituted of a set of partial differential equations, including electromagnetic equations, semiconductor physics and thermal equations. For accurately simulating temperature distributions in semiconductor devices, the thermal boundary conditions are researched in this paper. A commercial Schottky diode with model number HSMS-282c is excited by a 2 V step pulse generator. Its temperature variation under different thermal boundary conditions are compared. The diodes surface temperature under different forward voltage is also measured and compared with the simulation result. The results show that the temperature of semiconductor devices can be accurately simulated by the multiphysics algorithm with convection boundary condition.